Hans Aberg wrote:> However an elegant method, I am told that it hard to use in debugging,> as it is difficult for humans to interpret. So in actual functional> language implementations, it has not been used so much.

This is really no different than the problem of tracking source level
variables in the optimized assembly. A tedious task for humans, but
that's what compilers use symbol debugging entries (eg. DWARF2) for.

If it sees little application in practice it may have more to do with
the fact that it's still only a step on the road to an efficient
implementation.